Technological Field
The present invention relates to an ultrasonic probe and an ultrasonic diagnostic apparatus including the ultrasonic probe.
Description of the Related Art
By applying an ultrasonic probe connected to an ultrasonic diagnostic apparatus or communicable with the ultrasonic diagnostic apparatus to a body surface of a subject including human being and other animals or inserting the ultrasonic probe into the body, the ultrasonic diagnostic apparatus can obtain the shape, movement, or the like of a tissue as an ultrasonic diagnostic image. The ultrasonic diagnostic apparatus can repeatedly perform an examination advantageously because of high safety.
The ultrasonic probe incorporates, for example, a piezoelectric element that transmits and receives an ultrasonic wave. The piezoelectric element receives an electric signal (transmission signal) from the ultrasonic diagnostic apparatus, converts the received transmission signal into an ultrasonic signal to transmit the ultrasonic signal, receives an ultrasonic wave reflected in a living body to convert the ultrasonic wave into an electric signal (reception signal), and transmits the reception signal converted into the electric signal to the ultrasonic diagnostic apparatus.
The ultrasonic probe usually has an acoustic matching layer having an acoustic impedance with a magnitude between an acoustic impedance of the piezoelectric element and an acoustic impedance of a living body on a living body side of the piezoelectric element. The acoustic matching layer matches an acoustic impedance between the piezoelectric element and a subject (living body), and can make resolution of an ultrasonic diagnostic image to be obtained higher.
JP 2001-285995 A describes an ultrasonic probe having a conductor layer for applying a voltage to a piezoelectric element disposed between the piezoelectric element and an acoustic matching layer. According to JP 2001-285995 A, by disposing the conductor layer between the piezoelectric element and the acoustic matching layer, a range of selection of a material that can be used as the acoustic matching layer is broadened, and it is possible to manufacture the acoustic matching layer having an acoustic impedance capable of obtaining an ultrasonic diagnostic image with higher resolution. In addition, JP 2001-285995 A describes that the conductor layer may be formed of any material such as copper, nickel, aluminum, gold, or silver as long as having a small electric resistance.
As described in JP 2001-285995 A, if a conductor layer is disposed between a piezoelectric element and an acoustic matching layer and a material of the acoustic matching layer is appropriately selected, it is expected that an ultrasonic diagnostic image with higher resolution will be obtained. However, there is still a demand for further enhancing resolution of an ultrasonic diagnostic image. Therefore, development of an ultrasonic probe that can obtain an ultrasonic diagnostic image with higher image quality has been demanded.